1. Field of the Invention
This invention pertains to gas metal arc welding (GMAW), and more particularly to nozzles that direct an inert gas around GMAW arcs.
2. Description of the Prior Art
The gun of a gas metal arc welding (GMAW) system typically includes a nozzle that surrounds a gas diffuser and a contact tip. A weld wire is fed out of the contact tip. Electrical current conducted to the weld wire from the gas diffuser and the contact tip enables an arc to be struck and maintained between the weld wire and a workpiece. An inert gas is pumped through and out of the gas diffuser near the contact tip. A nozzle directs the gas to surround the weld wire and thus shield the welding arc from the atmosphere.
The spatial relationship between the ends of the contact tip and the nozzle is important, and that relationship varies with different welding jobs. Depending on the particular welding application, it may be desirable for the end of the contact tip to extend out past the end of the nozzle. In other applications, it may be better that the end of the contact tip be recessed inside the nozzle. Accordingly, it is well known to make the nozzle adjustable on the gun, usually by enabling the nozzle to slide on the gas diffuser.
FIGS. 1 and 2 show a portion of a prior mig welding gun 1 in which a nozzle 3 is axially slidable over rings 5 on a tubular insulator 7. The insulator 7 is pressed onto a gas diffuser 9. A contact tip 11 is secured to the gas diffuser 9. In FIG. 1, the nozzle 3 is pushed completely onto the insulator 7 such that a beveled shoulder 13 contacts the front end 15 of the insulator. In that situation, the nozzle is at a positive stop and is at a location where the end 17 of the contact tip 11 protrudes from the end 19 of the nozzle. In FIG. 2, the nozzle is pulled away from the positive stop and partially off the insulator 7 to a typical location at which the contact tip end 17 is recessed inside the nozzle. It is thus seen that the nozzle acts against a positive stop at only one location of the nozzle on the gas diffuser.
U.S. Pat. No. 2,659,797 describes another arc welding gun having a nozzle that acts against a positive stop at one location of the nozzle.
U.S. Pat. No. 5,380,980 discloses an adjustable slip-fit welding nozzle in which the nozzle acts against a positive stop for all locations of the nozzle on a gas diffuser.
A welding gun is desired that has more than one positive stop for a nozzle but the nozzle is not in contact with the positive stops at all nozzle locations.